The benefit of docker for home assistant is the packaging of it, rather than isolation. You can always run a container with host network mode and privileged mode so that it can access everything it needs to the same as if it were running directly on the host.

Overlooked option for running these things in containers is macvlan networking. Just give it its own MAC address on the network. Works great and you don't have to compromise on isolation.

You can get mDNS working in Docker, but IMO it's much easier to give up and use host networking. It is _very_ difficult to get mDNS working in K8s.

As an alternative to host network mode, you can give the container a dedicated IP on your network using the macvlan driver.

I've ditched all ARP, mDNS in my setup. Everything is static IP addresses: it vastly improved robustness against network glitches, which absolutely will happen to you.

If my router is unplugged or offline, everything with power can still communicate for example.

Nearly everything is static on mine too. I keep track of all the various devices' MAC addresses and assign them one IP. I also make sure that, even should I reinstall an OS on a device and "forget" to assign it a static IP, my router always assigns that MAC address the static IP I picked for that MAC address. I then keep a little range of IP addresses for unknown devices that the router is allowed to use when a new device shows up. Once in a while I log into my router and look which new device(s) I forgot to assign a static IP too.

When you say you ditched all ARP, did you do anything special? For example do you configure, on all your machines, static ARP entries for each MAC address of all your devices?

Sorry what I meant was I don't depend on any dynamic discovery systems like inspecting ARP tables.

I think it can, if you run your Docker containers in host network mode. I run my HA in docker using host mode, and it auto-detects all new devices that pop up on my network.

You can run in host network mode to avoid that.